Trench shoring machine

ABSTRACT

Upper and lower generally rectangular boxes, affixed together, are disposed in a trench to provide a safe working space for workmen installing underground pipe. Probing side plates at the front of the boxes are movable forward and backwards hydraulically to control collapse of the trench wall ahead of the box assembly. An upstanding pusher wall at the rear end of the upper box is hydraulically drivable rearwardly to push against fill in the trench behind the box assembly whereby, upon compaction, the box assembly is pushed forward in the trench. A shroud affixed to the rear of the lower box below the pusher wall assembly covers and protects the pipe from separation as the box assembly is moved forward. The box side walls are tapered inwardly toward the rear to minimize soil adhesion resistance to forward movement of the box assembly. Hydraulic lifting pads under the assembly assist in steering and maintenance of proper leveling and grade of the box assembly. Balancing and phasing means are provided in the hydraulic system. A built-in greasing system is employed.

0 United States Patent 1 1 1 1 3,715,889 Bixler et al. 1 Feb. 13, 1973[54] TRENCH SHORING MACHINE [76] Inventors: Donald Bixler, 9520 CopleyDr., ln- [57] ABSTRACT dlallapolls, Illd- 46260; Robert Upper and lowergenerally rectangular boxes, affixed y 6933 T011816) DR, lndltogether,are disposed in a trench to provide a safe allapollslllld- 46256 workingspace for workmen installing underground [22] Filed: Dec 3, 1971 pipe.Probing side plates at the front of the boxes are movable forward andbackwards hydraulically to con- [21] Appl- 204,437 trol collapse of thetrench wall ahead of the box assembly. An upstanding pusher wall at therear end of 52 us. (:1. ..6l/41 A, 6l/63 the upper box is hydraulicallydrivable reerwardly 51 1m. (:1. .E2ld 5/12 P against fill in the trenchbehind the box assembly [58] Field of Search ..61/41, 41 A, 63, 84, 85,72.2 whereby, p compaction, the box assembly is pushed forward in thetrench. A shroud affixed to the [56] References Ci d rear of the lowerbox below the pusher wall assembly covers and protects the pipe fromseparation as the UNITED STATES PATENTS box assembly is moved forward.The box side walls are 2,908,140 10/1959 Everson ..61/41 A taperedinwardly Ward the Year minimize 30g9,310 5/1963 Toni "61/41 A hesionresistance to forward movement of the box as- 3,473,336 10 1969 Toni "514 A sembly. Hydraulic lifting pads under the assembly 3,479,827 11/1969Morrice.... 61/63 X assist in steering and maintenance of properleveling 3,543,522 12/1970 Torti l i ..6l/85 and rade of the boxassembly. Balancing and phasing 3,608,319 9/1971 Quitadamo ..6l/63Primary ExaminerDennis L. Taylor Attorney-Joseph A. Naughton, Jr.

means are provided in the hydraulic system. A built-in greasing systemis employed.

21 Claims, 8 Drawing Figures PATENTEUFEB l 3 I975 sum 2 0F 3 FIG. 5

FIG. 4

TRENCH SHORING MACHINE BACKGROUND OF THE INVENTION aware will beprovided at the end of this specification.

Some of the references are rather primitive by todays standards, butthat is understandable in view of the early dates at which suchreferences came into existence. More recent developments shown in thereferences include shoring machines which use a hydraulic power supplyfrom an external source for driving hydraulic pistons and thereby makingthe shoring machines self-propelled in the trench. However, to provideadequate working space in the trench and yet adequately protect theworkmen both from the digging equipment and from cave-ins, the prior artmachines are of substantial length and some, such as the Torti machines,are closed on top. These characteristics add to weight, thus making themachine more difficult to transport on a truck or trailer to the worksite, and more difficult to move and control in the trench. Also therehave been problems encountered as a result of adhesion of soil to thesides and rear of the shoring machines as they move forward or as thepusher element is retracted forwardly, with attendant problems oftroublesome advancement in the trench and tendency to separate assembledlengths of pipe. The present invention is directed to overcoming theseproblems encountered with prior art equipment.

SUMMARY OF THE INVENTION Described briefly, in a typical embodiment ofthe present invention, a shoring machine is somewhat boxlike assemblyhaving a generally upstanding pusher wall at the upper rear end thereof,and which is movable back and forth by powered actuator means. The lowerrear wall is stationary with respect to the side walls and is providedwith a shrouded opening to protect the work which has been done.

Powered probing plates on the sides of the machine at the front end aremovable forwardly and retractable independent of the main body of theshoring machine, to support the sides of the trench as it is being dugand continue such support during forward movement of the shoring machineitself by actuation of the pusher wall rearwardly. Powered selectivelyoperable lifting pads are provided at the bottom to aid in steering theassembly and to maintain the proper level of the box and hold the propergrade.

Means are provided to assure equal movement of actuator means,simplification of lubrication, and minimize weight, and remove waterfrom the trench.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of a shoringmachine according to a typical embodiment of the present invention.

FIG. 2 is a side elevational view thereof.

FIG. 3 is a section therethrough taken at line 3-3 in FIG. 1 and viewedin the direction of the arrows.

FIG. 4 is a front end view thereof.

FIG. 5 is a fragmentary front end view showing the assembly tilted byone of the lifting pads, and with the front wall of the lower box of themachine omitted to show the pad operating cylinders.

FIG. 6 is a schematic hydraulic diagram of the machine.

FIG. 7 shows the machine in a trench.

FIG. 8 is a schematic mechanical diagram of the probing plate guidegreasing system.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings indetail, as shown in FIG. 1, the shoring machine is a generallyrectangular structure, and as indicated in FIG. 2, may be regarded as abox assembly including a lower box 11 and an upper box 12 securedtogether. Neither of these socalled boxes has a top or bottom. The lowerbox has a rear end wall 13 with a shroud 14 affixed thereto andextending rearwardly therefrom covering a portion of the'sewer pipe 16which has been installed by workmen working in the unit at 15. The lowerbox has a front end wall 17 (FIG. 3). The upper box is open in front.

The upper box 12 has a pusher unit therein including a rear end wall 18which is movable rearwardly in the direction of arrow 19 and forwardlyin the direction of arrow 21 by hydraulic cylinders 22 (FIG. 3). Thepusher unit includes a pair of side walls 23 and a top wall 24 affixedto pusher wall 18, this entire assembly being movable as a unitindependent of the box assembly.

At the front of the boxes and immediately outside of the side walls ofthe boxes there are probing plates. While upper probing plates in oneform were used by us on a predecessor machine more than a year ago, wehave since determined that additional probing plates are needed. Forexample, according to the present invention, on each side there areupper, intermediate, and lower probing plates 26, 27 and 28,respectively. Each of these plates is drivable forwardly in thedirection of arrow 21 and rearwardly in the direction of arrow 19 bymeans of hydraulic cylinders 29 (FIG. 3).

Probing plate 26 is affixed to the front end of each of three tubes 31,32, and 33, as at 34, for example. Tube 1 31 serves as a guide tubelinearly slidable inside a guide sleeves 36 affixed in the wall 37. Thestructure of wall 37 to facilitate such attachment can include aplurality of channel sections 38 extending lengthwise of the machinebetween the inner and outer wall sheeting 39 and 41, respectively andwelded thereto. Vertical webs 42 are provided between the channels andthe wall sheeting and are welded to the channels. This is also shownschematically in FIG. 8 wherein two of the vertical webs (identified 42Aand 42B) cooperate with the wall sheeting and channels 38 to form aplurality of grease boxes (as at 40 for tube 31), one for each tube. Aseparate grease line is provided for each of the boxes, and the sixlines for the six boxes shown in FIG. 8 terminate in the group of greasefittings 45 conveniently located at the top of the wall 37. Each of theguide sleeves such as 36 opens into a respective one of the grease boxesand, of course, the guide tubes such as 31 are openly exposed to thegrease packing the boxes through which they extend. The guide sleevessuch as 36 can be welded to the webs 42. The same kind of mounting canbe provided for the sleeves 43 and 44 guiding the tubes 32 and 33,respectively. A universal joint 46 provides the connection between thetube 32 and the piston rod 37 of cylinder 29 for probing plate 26.Therefore, as the cylinder 29 drives the probing plate 26 forward orbackward, tubes 31 and 33 in sleeves 36 and 44 serve guiding functionsand while tube 32 is guided in sleeve 43, the universal joint 46 removesany possibility of binding due to any misalignment which might exist ordevelop between the tube 32 and piston rod 47. Cylinder 29 is confinedin the wall 37 by webs such as 42, but is not welded thereto, the rearend thereof being anchored to pin 48 which may be mounted in two of thechannel members 38.

For the pusher wall, as best shown in FIG. 3, there are two right-handpusher cylinders 22 each pinned as at 49 to brackets 51 affixed to theinner wall 39 and thereby to the elongated channels 38 of the upper boxassembly. The piston rods 52 are connected by universal joints 53 to thepusher wall 18, with whatever the enforcement may be needed at theregion of thrust. An upper guide tube 56 is affixed to the pusher wallas is a lower guide tube 57 and, as described for the guide tubes of theprobing plates, there are short sections of guide sleeves affixed in thewall 37 tittingly and slidingly receiving these guide tubes 56 and 57.The same construction is provided on the left-hand side of the shoringmachine. The total of four guide tubes in guide sleeves thereformaintains proper alignment of the pusher wall as it is pushed rearwardlyby the cylin ders 22 and, as it is retracted to permit fill to bedeposited behind the shoring machine.

To assist in steering and leveling and maintaining the proper grade withthe shoring machine, lifting pads 61 and 62 are provided near the frontof the machine. Each of these pads ishinged at its front end to thelower front end of the shoring machine as at hinge pin 63 for pad 62 inFIG. 3. Each pad also has an actuating cylinder as at cylinder 64 forpad 62. The upper end of this cylinder is pinned at 66 to a bracketaffixed to crossmember 67 affixed to the inside wall of the shoringmachine. The piston rod 68 is pinned at 69 to a bracket affixed to thepad 62. FIG. 3 and FIG. 4 show both pads actuated by extending thepiston rods of their respective cylinders. FIG. shows only theright-hand pad actuated to illustrate the tilting function which can beeffected. The pads are retracted in FIGS. 1 and 2.

In the lower box, forprobing plate 28 both of the mounting tubes aredriven by cylinders 29, in contrast to the arrangement for the upperplates in the upper box wherein for each there are two guide tubes and-apushing tube.

As shown in FIGS. 1 and 2, there is a cross over walkway and observationplatform 71 near the front end of the upper box. As best shown in FIGS.2 and 3, there is an operators platform 72 near the rear end of themachine but this platform is omitted from FIG. 1 in order to enableshowing the top cover 24 of the pusher wall assembly. At the operatorsplatform there is a plurality of controls as indicated onlysymbolicallyby handle lever 73 in FIG. 2. The hydraulic diagram of FIG. 6 shows thevarious controls and associated hydraulic circuitry.

Referring now to FIG. 6, a reservoir 74 of hydraulic fluid servesconstant displacement pumps 76 and 77. Each of these pumps has apressure relief valve associated therewith and return line to thereservoir. Pump 76 has a pressure output on line 78 to the first mastercontrol valve 79. This valve is shown in a neutral position blockingflow from a pump 76 to a series of probing plate control valves 81.

Similarly, pump 77 has a pressure output on line 82 connected to asecond master control valve 83. The connection to this valve is suchthat, in the neutral position shown, pressure is provided from pump 77through valves 83, 84, 86 and 87 back to the reservoir on return line88.

Valve 79, when shifted to the left, will direct pressure from pump 76through each of the eight valves 81 for the probing plates, back to thereservoir on return line 89. Each of the valves 81 is shiftable one stepto the left from the neutral position shown, to provide for extension ofthe piston rod of the corresponding cylinder 29, or is shiftable onestep to the right to provide retraction of the piston rod. Upon shiftingthe valve two steps to the left, chambers at both ends of the pistoncommunicate with one another through the valve and the piston can moveeither way therein, depending upon the load thereon. This is a floatingposition.

When valve 83 is in the position shown, valve 84 can be shifted to theleft to extend the piston rods from the respective push cylinders 22,and shifting the valve to the right will serve to retract the pistonrods in cylinders 22. Moving either of the lift cylinder control valves86 or 87, to the left will extend the piston rod of the correspondinglift cylinder; and moving the valve to the right will retract the pistonrod of the corresponding lift cylinder.

Shifting the first master control valve 79 to the right will providepressure from pump 76 through valve 79, line 91 and check valve 92 tothe second control valve 83. In this position it can supplement thesupply from pump 77. Similarly, shifting the second master control valve83 to the left will provide supply from the pump 77 through valve 83,line 93 and check valve 94 to valve 79 to supplement the supply theretofrom pump 76.

Four hydraulically driven rotary motors 96 of fixed displacement havecommonly connected shafts and each has an input port hydraulicallyconnected to a port of one of the push cylinders. Each input port isalso connected through one of the relief valves 97 to the return line98, 88 to the sump 74. The comparatively positive and fixeddisplacement, and mechanical inter-connection of these motorscontributes to uniform travel of the piston rods of the various pushcylinders 22. Thus, they serve as a sort of flow divider or equalizer.The P4759 flow divider produced by Delta Mfg. Co. was used for thispurpose.

The possibility of using both pumps 76 and 77 to serve a set of valvesprovides an effective pumping source of volumetric capacity twice thatavailable from a single one of the pumps.

OPERATIONS In the operation of the apparatus, and referring to FIG. 7, aconventional digging machine makes a hole in the ground of the properdepth for the work to be done. While the machine is useful for variouskinds of work, one example is the laying of sewer pipe. For thispurpose, the hole is dug to the depth at which the pipe is to be laid.Then the shoring machine is lowered into the hole by the use of a craneand appropriate connecting cables. The workmen then climb down insidethe machine to the bottom of the trench. Lengths of sewer pipe arelowered individually by a crane when needed through the open top to theworkmen below. They assemble a length of pipe with the preceding length,a portion of which is shown projecting out under the rear end shroud 14.Meanwhile backfill material is moved into the hole behind the shoringmachine at 102, by a shovel, dozer or other equipment. The probingplates 26, 27, and 28 are moved forward hydraulically as the pipeassembly progresses, to prevent collapse of the bank of the trench aheadof the machine, as the trench is lengthened by the digging machine.Typically the probing plate drive cylinders have a stroke of about 6feet, while the length of the working space in the machine and in whichthe workmen can work is approximately l4 feet. The front wall of thespace is approximately 6 feet high.

When the length of pipe has been installed, the valves for the probingplates are placed in the furthermost position to the left (FIG. 6),placing the cylinders in the floating condition. Valve 84 (FIG. 6) isshifted to the left which applies pressure to the push side of the pushcylinders 22. This forces the pusher wall to the rear in the directionof arrow 19 against the flll material which has been placed behind theshoring machine. This compacts the material and, when sufficientcompaction has been established, additional travel of the pusher wallwith respect to the shoring machine will thrust the shoring machineforwardly in the direction of arrow 21. As it so moves, the probingplates float toward their original retracted position. In the event thefill is so loose as to fail to provide sufficient resistance to move themachine forwardly the desired amount for installation of the next lengthof pipe, the pusher wall can be retracted, additional fill moved inbehind it, and the process repeated. Eventually the machine will havebeen moved forward sufficiently for addition of another length or two ofsewer pipe.

Once forward movement of the machine to the desired extent has beenaccomplished, valve 84 is shifted to the neutral position shown in FIG.6, and one or more of the valves for the probing plates can be shiftedas needed to extend the probing plates in the direction of arrow 21 andthus protect against cave-ins of the trench wall ahead of the machinefor an additional 6 feet or so. As suggested above, if the mastercontrol valve 83 is moved to the left, twice the volume of hydraulicfluid available with the one pump can be provided, to double the speedat which the advance of the probing plates can be accomplished.

During the advancement of the shoring machine, if some adjustment isneeded in the attitude or direction thereof, valve 86 or 87 can beshifted as needed to operate one or both of the lifting pads.

If water in the trench bottom is a problem, a pump 106 driven byhydraulic motor 104 and having water intake hose 107 connected to itsintake, is employed. The hose is extended to an intake screen 108 at thebottom of the trench and ahead of the machine, or it may be locatedwherever desired to best serve its purpose of keeping the trench dry.Valve 109 controls motor 104.

The reservoir and pumping equipment for the hydraulic fluid may be on aseparate self-propelled or tractor-drawn wagon on the surface of theground at the side of the trench, with appropriate plumbing to thecontrol desk 72.

As best shown in FIG. 1, the probing plates are immediately outside theoutside wall sheets of the machine. The spacing between the walls at thefront is greater than at the rear. The pusher unit is within the outerwall sheets at the rear, as best shown in FIG. 1. Thus, in addition tothe fact that there is 'a greater horizontal dimension between the outerwall sheets at the front than at the rear, thus providing a taper of thebox toward the rear, the arrangement of the probing plates outside andthe pusher unit to the inside, further emphasizes the tapered aspect,facilitating forward movement of the box in the trench. In addition,because of the taper, the front edges of the probing plates are fartherapart horizontally when the plates are extended, than when the platesare retracted. Therefore, as the shoring machine is pushed ahead, andthe probing plates float, the machine is moved into a space which isactually wider than is the front end of the machine itself with theplates retracted.

The facts that the pusher wall is above the aperture in the rear of themachine, and the shroud covering the aperture at the rear extendsrearwardly the full extent of the pusher wall travel, assures that therewill be no adhesion of back fill material or soil to the pipe. Thebenefit of this is avoidance of pulling joints apart during forwardmovement of the machine.

It can be seen that the shoring machine of the present invention mightemploy expanded metal for the side plates to afford protection of themen working in the machine, and yet secure a substantial weight saving.The various horizontal struts provide a rather open construction of theassembly, and substitution of longer struts would facilitate wideningthe overall assembly, and vice versa.

The employment of universal joints at the end of the pushing ramsadjusts for any unequal movement of the side pushing rams. If, on thereturn stroke, one piston bottoms out before another one, continuedsupply of hydraulic fluid to the other pistons will return them to thehome or bottom out condition so that they can all advance together fromthe same position upon commencement of the next extension of the pusherunit and are, therefore, starting in phase with each other. For thepiston which bottoms-out" first, any pressure build up resulting fromfluid leakage through the motor 96 associated therewith, while theremaining pistons continue to move, can escape through that one of thepressure relief valves 97 associated with the cylinder which hasbottomed out." The pressure setting for valves 97 is preferably belowthe pressure setting for the relief valves at the pumps. This settingwill depend on the size and weight and performance requirements of theequipment.

The prior art patents known to us and referred to above are UnitedStates patents as follows:

654,426 Washington July24, 1900 977,016 Johnson November 29, i9101,234,716 Bager July 31,1917 1,305,270 Farrar June 3, 1919 1,817,367Greiman August 4, 1931 1,896,433 Windeknecht February 7, 1933 2,633,713Shields April 7, 1953 2,865,178 Wicke December 23, 1958 2,866,320Bazzell December 30, 1958 2,908,140 Everson, Jr. October 13, 19592,922,283 Porter January 26, 1960 3,089,310 Torti May 14, 1963 3,l59,978De Lillo December 8, 1964 3,204,415 Hill, Jr. et al September 7, 19653,377,806 Morrice April 16, I968 3,420,065 l-loll January 7, 19693,473,336 Torti October 21, 1969 3,479,827 Morrice November 25, 1969While the invention has been disclosed and described in some detail inthe drawings and foregoing description, they are to be considered asillustrative and not restrictive in character, as other modificationsmay readily suggest themselves to persons skilled in this art and withinthe broad scope of the invention.

The invention claimed is:

1. A trench shoring machine comprising:

a base frame supportable on the bottom of a trench and havinghorizontally spaced upstanding side walls disposed to prevent collapseof the trench bank into the space at the bottom of the trench betweensaid side walls;

pusher means including a generally upstanding pusher wall transverse tosaid side walls at the upper rear end of said base frame and linearlymovable with respect to said base frame;

a lower rear end wall on said base frame and fixed with respect to saidside walls and having an opening therein to accommodate forward movementof said base frame lengthwise in said trench without disturbance of workcompleted in said trench between said side walls.

2. The shoring machine of claim 1 wherein:

said pusher means include actuator means mounted on said base frame andoperable, when actuated, to drive said pusher wall rearwardly withrespect to said base frame to a point of substantial rearward projectiontherefrom;

said rear end wall having a shroud extending rearwardly under a portionof the region of rearward projection of said pusher wall and around theupper margin of said opening to cover said work projecting through saidopening and to preclude such adhesion of soil behind said frame to saidframe and said work as would disturb said work as said frame is movedforward lengthwise in the trench.

3. The combination of claim 2 wherein:

said shroud is a downwardly and rearwardly opening hood for coverage ofthe top and sides of the said work without complete encirclement of thework.

4. The machine of claim 1 wherein:

the spacing between said side walls is greater at the front end of saidbase frame than at the rear end of said base frame to alleviatefrictional resistance from horizontal soil pressure during forwardmovement of said frame.

5. The machine of claim 1 and further comprising:

first and second lifting pads disposed at the bottom of said base frameand mounted thereto for operation from' first positions between saidside walls to second positions inclined downwardly and rear-- wardlyfrom the bottom of said base frame. The machine of claim 5 and furthercomprising:

first and second actuator means coupled to said base frame and coupledrespectively to said first and second pads and operable independently ofeach other for obtaining different extents of downward inclination toassist in steering said base frame as it moves forwardly in said trench.

7. The combination of claim 1 wherein said pusher means include:

a plurality of slides and a plurality of guides mounted respectively tosaid pusher wall and to said base frame, said slides being guidinglyreceived in said guides for linear movement of said slides rearwardlyand forwardly on said base frame, and

linear actuator means mounted to said base frame and coupled to one ofsaid slides to drive said one slide, and thereby said pusher wall,rearwardly, from a retracted position to an extended position.

8. The combination of claim 7 wherein said pusher means include:

a universal joint connecting one of said slides to said pusher wall.

9. The combination of claim 8 wherein said linear actuator meansinclude:

a first cylinder mounted to one of said side walls and having a pistonrod connected to one of said slides; and

a second cylinder mounted to the other of said side walls and having apiston rod connected to another of said slides,

both of said cylinders being double acting,

a source of hydraulic pressure,

valve ,means operable in an advance position to supply hydraulic fluidfrom said source to one side of a piston in each of said cylinders toextend said pusher wall to drive said base frame forward;

said valve means being operable in a retract position to supplyhydraulic fluid to the opposite side of said piston in each of saidcylinders and release fluid on said one side of said piston, to retractsaid pusher wall,

and equalizing means operable to establish uniform movement for both ofsaid pistons during movement of said pusher wall.

10. The combination of claim 7 wherein:

said side walls at the upper rear end of said base frame include outerside plates; and

said pusher means include outer side walls disposed immediately insidesaid outer side plates when said pusher wall is retracted.

11. The combination of claim 10 wherein:

said pusher means include a top wall, said side and top walls of saidpusher means being joined to top and side margins, respectively, of saidpusher wall.

12. The combination of claim 11 wherein:

said base frame has a lower front end wall extending up to a level abovethe level of the top of the opening in said lower rear end wall.

13. The combination of claim 1 and further comprising:

probing plates, one of said platesbeing located at the front of each ofsaid side walls,

said plates being movable forwardly independently of said side walls tocontrol collapse of trench walls ahead of said side walls.

14. The combination of claim 13 wherein:

each of said probing plates overlaps a portion of the side wall at whichit is mounted, both before and after forward movement of said plate.

15. The combination of claim 14 and further comprising:

plate drive means coupled to said plates;

said pusher means including pusher drive means coupled to said pusherwall, and

control means coupled to said plate drive means and to said pusher drivemeans to enable simultaneous powered forward movement of said plates andpusher wall with respect to said base frame, and simultaneous rearwardmovement of said plates and pusher wall with respect to said base frame.

16. The combination of claim 14 wherein:

said pusher drive means include hydraulic actuators, and a source ofhydraulic pressure therefor, and

' said plate drive means including hydraulic probing plate driveactuators, and a source of hydraulic pressure therefor;

said control means include a first control valve having a firstcondition hydraulically locking said actuators for said pusher drivemeans, and having second and third positions for respectively extendingand retracting said pusher wall; and

said control means include additional control valves, each having afirst position hydraulically locking the said probing plate driveactuator coupled thereto, and each having second and third positions forrespectively power retracting and power extending the probing platedrive actuator coupled thereto, and each having a fourth positionhydraulically neutralizing said probing plate drive actuator coupledthereto to permit the probing plate associated therewith to float inaccord with external loads encountered thereby.

17. A trench shoring machine comprising:

a base frame supportable on the bottom of a trench and havinghorizontally spaced upstanding side walls disposed to prevent collapseof the trench bank into the space between said walls;

pusher means at the upper rear of said base frame and movable rearwardlyand forwardly with respect to said base frame;

probing plates at the front of said base frame immediately outside theouter faces of said side walls from a point near the bottom of said baseframe to a point near the top of said base frame, said probing platesbeing movable forwardly and rearwardly with respect to said base frame.

18. The shoring machine of claim 17 wherein:

said pusher means include pusher drive means; and

plate drive means are connected to said plates.

19. The machine of claim 18 wherein:

said pusher drive means include hydraulic actuators, and a source ofhydraulic pressure therefor, and said plate drive means includehydraulic probing plate drive actuators, and a source of hydraulicpressure therefor;

the machine further comprising control means including a first controlvalve having a first condition hydraulically locking said actuators forsaid pusher drive means, and having second and third positions forrespectively extending and retracting said pusher means; and saidcontrol means lllClUdll'lg additional control valves, each having afirst position hydraulically locking the said probing plate driveactuator coupled thereto, and each having second and third positions forrespectively power retracting and power extending the probing platedrive actuator coupled thereto, and each having a fourth positionhydraulically neutralizing said probing plate drive actuator coupledthereto to permit the probing plate associated therewith to floatforwardly or rearwardly in accordance with external loads encounteredthereby.

20. A method of shoring a trench including the steps of placing ashoring machine inside a trench, projecting separately movable probingplates forward from the sides of said shoring machine adjacent thetrench banks in front of the machine;

projecting a pusher wall from the rear of said machine against fill inthe trench behind the machine and thereby moving the machine forward,and permitting the probing plates to remain in position with respect tothe trench wall as the shoring machine is pushed forward by the pusherwall; and retracting the pusher wall and extending the probing platesforward again from the front of the machine as the machine remains atrest in the trench. 21. The method as set forth in claim 20 and furthercomprising the step of:

depressing movable support means at the bottom of the shoring machineagainst the bottom of the trench to raise the front of the shoringmachine.

1. A trench shoring machine comprising: a base frame supportable on thebottom of a trench and having horizontally spaced upstanding side wallsdisposed to prevent collapse of the trench bank into the space at thebottom of the trench between said side walls; pusher means including agenerally upstanding pusher wall transverse to said side walls at theupper rear end of said base frame and linearly movable with respect tosaid base frame; a lower rear end wall on said base frame and fixed withrespect to said side walls and having an opening therein to accommodateforward movement of said base frame lengthwise in said trench withoutdisturbance of work completed in said trench between said side walls. 1.A trench shoring machine comprising: a base frame supportable on thebottom of a trench and having horizontally spaced upstanding side wallsdisposed to prevent collapse of the trench bank into the space at thebottom of the trench between said side walls; pusher means including agenerally upstanding pusher wall transverse to said side walls at theupper rear end of said base frame and linearly movable with respect tosaid base frame; a lower rear end wall on said base frame and fixed withrespect to said side walls and having an opening therein to accommodateforward movement of said base frame lengthwise in said trench withoutdisturbance of work completed in said trench between said side walls. 2.The shoring machine of claim 1 wherein: said pusher means includeactuator means mounted on said base frame and operable, when actuated,to drive said pusher wall rearwardly with respect to said base frame toa point of substantial rearward projection therefrom; said rear end wallhaving a shroud extending rearwardly under a portion of the region ofrearward projection of said pusher wall and around the upper margin ofsaid opening to cover said work projecting through said opening and topreclude such adhesion of soil behind said frame to said frame and saidwoRk as would disturb said work as said frame is moved forwardlengthwise in the trench.
 3. The combination of claim 2 wherein: saidshroud is a downwardly and rearwardly opening hood for coverage of thetop and sides of the said work without complete encirclement of thework.
 4. The machine of claim 1 wherein: the spacing between said sidewalls is greater at the front end of said base frame than at the rearend of said base frame to alleviate frictional resistance fromhorizontal soil pressure during forward movement of said frame.
 5. Themachine of claim 1 and further comprising: first and second lifting padsdisposed at the bottom of said base frame and mounted thereto foroperation from first positions between said side walls to secondpositions inclined downwardly and rearwardly from the bottom of saidbase frame.
 6. The machine of claim 5 and further comprising: first andsecond actuator means coupled to said base frame and coupledrespectively to said first and second pads and operable independently ofeach other for obtaining different extents of downward inclination toassist in steering said base frame as it moves forwardly in said trench.7. The combination of claim 1 wherein said pusher means include: aplurality of slides and a plurality of guides mounted respectively tosaid pusher wall and to said base frame, said slides being guidinglyreceived in said guides for linear movement of said slides rearwardlyand forwardly on said base frame, and linear actuator means mounted tosaid base frame and coupled to one of said slides to drive said oneslide, and thereby said pusher wall, rearwardly, from a retractedposition to an extended position.
 8. The combination of claim 7 whereinsaid pusher means include: a universal joint connecting one of saidslides to said pusher wall.
 9. The combination of claim 8 wherein saidlinear actuator means include: a first cylinder mounted to one of saidside walls and having a piston rod connected to one of said slides; anda second cylinder mounted to the other of said side walls and having apiston rod connected to another of said slides, both of said cylindersbeing double acting, a source of hydraulic pressure, valve meansoperable in an ''''advance'''' position to supply hydraulic fluid fromsaid source to one side of a piston in each of said cylinders to extendsaid pusher wall to drive said base frame forward; said valve meansbeing operable in a ''''retract'''' position to supply hydraulic fluidto the opposite side of said piston in each of said cylinders andrelease fluid on said one side of said piston, to retract said pusherwall, and equalizing means operable to establish uniform movement forboth of said pistons during movement of said pusher wall.
 10. Thecombination of claim 7 wherein: said side walls at the upper rear end ofsaid base frame include outer side plates; and said pusher means includeouter side walls disposed immediately inside said outer side plates whensaid pusher wall is retracted.
 11. The combination of claim 10 wherein:said pusher means include a top wall, said side and top walls of saidpusher means being joined to top and side margins, respectively, of saidpusher wall.
 12. The combination of claim 11 wherein: said base framehas a lower front end wall extending up to a level above the level ofthe top of the opening in said lower rear end wall.
 13. The combinationof claim 1 and further comprising: probing plates, one of said platesbeing located at the front of each of said side walls, said plates beingmovable forwardly independently of said side walls to control collapseof trench walls ahead of said side walls.
 14. The combination of claim13 wherein: each of said probing plates overlaps a portion of the sidewall at which it is mounted, both before and after forward movement ofsaid plate.
 15. The combination of clAim 14 and further comprising:plate drive means coupled to said plates; said pusher means includingpusher drive means coupled to said pusher wall, and control meanscoupled to said plate drive means and to said pusher drive means toenable simultaneous powered forward movement of said plates and pusherwall with respect to said base frame, and simultaneous rearward movementof said plates and pusher wall with respect to said base frame.
 16. Thecombination of claim 14 wherein: said pusher drive means includehydraulic actuators, and a source of hydraulic pressure therefor, andsaid plate drive means including hydraulic probing plate driveactuators, and a source of hydraulic pressure therefor; said controlmeans include a first control valve having a first conditionhydraulically locking said actuators for said pusher drive means, andhaving second and third positions for respectively extending andretracting said pusher wall; and said control means include additionalcontrol valves, each having a first position hydraulically locking thesaid probing plate drive actuator coupled thereto, and each havingsecond and third positions for respectively power retracting and powerextending the probing plate drive actuator coupled thereto, and eachhaving a fourth position hydraulically neutralizing said probing platedrive actuator coupled thereto to permit the probing plate associatedtherewith to float in accord with external loads encountered thereby.17. A trench shoring machine comprising: a base frame supportable on thebottom of a trench and having horizontally spaced upstanding side wallsdisposed to prevent collapse of the trench bank into the space betweensaid walls; pusher means at the upper rear of said base frame andmovable rearwardly and forwardly with respect to said base frame;probing plates at the front of said base frame immediately outside theouter faces of said side walls from a point near the bottom of said baseframe to a point near the top of said base frame, said probing platesbeing movable forwardly and rearwardly with respect to said base frame.18. The shoring machine of claim 17 wherein: said pusher means includepusher drive means; and plate drive means are connected to said plates.19. The machine of claim 18 wherein: said pusher drive means includehydraulic actuators, and a source of hydraulic pressure therefor, andsaid plate drive means include hydraulic probing plate drive actuators,and a source of hydraulic pressure therefor; the machine furthercomprising control means including a first control valve having a firstcondition hydraulically locking said actuators for said pusher drivemeans, and having second and third positions for respectively extendingand retracting said pusher means; and said control means includingadditional control valves, each having a first position hydraulicallylocking the said probing plate drive actuator coupled thereto, and eachhaving second and third positions for respectively power retracting andpower extending the probing plate drive actuator coupled thereto, andeach having a fourth position hydraulically neutralizing said probingplate drive actuator coupled thereto to permit the probing plateassociated therewith to float forwardly or rearwardly in accordance withexternal loads encountered thereby.
 20. A method of shoring a trenchincluding the steps of placing a shoring machine inside a trench,projecting separately movable probing plates forward from the sides ofsaid shoring machine adjacent the trench banks in front of the machine;projecting a pusher wall from the rear of said machine against fill inthe trench behind the machine and thereby moving the machine forward,and permitting the probing plates to remain in position with respect tothe trench wall as the shoring machine is pushed forward by the pusherwall; and retracting the pusher wall and extending the probing platesforward again frOm the front of the machine as the machine remains atrest in the trench.